WO2006075559A1

WO2006075559A1 - Communication method and reception terminal

Info

Publication number: WO2006075559A1
Application number: PCT/JP2006/300088
Authority: WO
Inventors: Eiichi Muramoto; Takahiro Yoneda; Toyoki Kawahara
Original assignee: Matsushita Electric Industrial Co., Ltd.
Priority date: 2005-01-11
Filing date: 2006-01-06
Publication date: 2006-07-20
Also published as: JP4567007B2; CN101103602B; CN101103602A; US20090285211A1; JPWO2006075559A1; US7924714B2

Abstract

When switching a terminal receiving streaming from a first reception terminal to a second reception terminal, it is possible to receive and reproduce the streaming immediately after the switching without break. A communication method for modifying the reception terminal performing rate control using TFRC from the first reception terminal to the second reception terminal includes: a judgment step for judging whether the route in a network between the streaming transmission terminal and the first reception terminal is identical to the route in a network between the transmission terminal and the second reception terminal; and a transmission step for transmitting history information on a packet loss managed by the first reception terminal to the second reception terminal if the routes are judged to be identical.

Description

Communication method and receiving terminal

Technical field

TECHNICAL FIELD [0001] The present invention relates to a communication method and a receiving terminal for changing a streaming receiving terminal that performs rate control using TFRC (TCP Friendly Rate Control) from a first receiving terminal to a second receiving terminal. .

Background art

[0002] (Internet definition)

Here, the network that connects the neighboring routers of each terminal is defined as the Internet. Specifically, when sending data to a terminal in another home, the data to be sent is sent from the home router to an access line such as an ADSL or optical line, or multiple ISP (Internet Service Provider) lines. Etc. are transmitted through. Furthermore, the data to be transmitted is delivered to the terminal in another home via the access line and home router for another home. The network from this home router to another home router is called the Internet.

[0003] It is difficult to secure a fixed bandwidth between any terminals connected to the Internet. Conventionally, INTSERV (Integrated Services) that reserves bandwidth for each communication between terminals using RSVP (Resource ReSerVation Protocol) is known as a method for reserving bandwidth between routers on the Internet! However, since the same method must be applied to all routers operated by multiple ISPs on the Internet, it has not been put into practical use. For this reason, on the Internet, communication between all terminals communicates while sharing the bandwidth.

[0004] TCP is widely used as a communication method for the communication between terminals to share the bandwidth fairly on the best F-Internet. This TCP is used for e-mail, WWW (World Wide Web), P2P (peer to peer) file exchange communications such as Winny and WinMX, and occupies most of the Internet traffic. For this reason, Best Fauto Internet communication shares the bandwidth fairly with this TCP. It is recommended to control the transmission rate and realize congestion control (Reference: "

Congestion Control Principles, RFC 2914).

On the other hand, TCP shows a characteristic called AIMD (Additive Increase Multiple Decrease) in transmission rate control. Because of this characteristic, the transmission rate changes dramatically, making it unsuitable for streaming in which continuous information such as audio and video is transmitted over a network.

[0006] In order to solve this problem, TFRC has been developed to share the bandwidth fairly with TCP while performing smooth transmission rate control.

[0007] TFRC is a method for controlling a transmission rate by estimating a transmission rate (X) that can share a bandwidth fairly with TCP based on a loss event rate (p) and a round trip time (R), which will be described later. Specifically, the transmission rate (X) is estimated using Equation 1 below.

[Number 1]

[0008] In transmission rate control using TFRC, transmission rate estimation using Equation 1 is performed each time a loss occurs (see Fig. 1).

[0009] In order to achieve smooth transmission rate control, the loss event rate (P) is based on loss information of the past several times (8 times in Fig. 1) in addition to this TFRC transmission rate control. Calculated.

[0010] By controlling in this way, TFRC achieves both high-speed congestion avoidance and smooth rate control when the Internet is in an excessively congested state. In other words, when congestion occurs on the Internet, many loss events occur in a short time. This immediately increases the loss event rate observed at the receiving terminal. By reporting this value to the sender at each loss, the transmission rate is immediately calculated and applied according to Equation 1, and the flow rate is reduced. As a result, it works as an Internet congestion avoidance. Conversely, if there is no excessive congestion on the Internet and there is not much loss, the frequency of loss will decrease and the loss event rate observed on the receiving side will gradually decrease. As described above, the loss event rate is calculated taking into account the loss history, so If this happens, the loss event rate decreases smoothly, and the transmission rate increases smoothly accordingly. In other words, when congestion occurs on the Internet, a high-speed congestion avoidance operation is performed, and when recovering from the congestion state, the transmission rate fluctuates (increased) smoothly.

[0011] Also, in TFRC, at the start of transmission, the operation of gradually increasing the transmission rate from the round-trip time of transmission rate = 1 packet Z is performed (referred to as slow start), as in TCP. However, since the transmission rate of TFRC varies smoothly compared to TCP, it takes a lot of time to reach the rate necessary for streaming. Also, streaming that is played while receiving data continuously cannot be played on the receiving side unless a transmission rate higher than the playback speed is secured. Therefore, for the receiving terminal, it takes a lot of time from the start of streaming reception to the actual start of video playback.

[0012] For this reason, when the user switches the receiving terminal to a new terminal having a specific terminal power, a lot of waiting time is required.

On the other hand, when streaming is transmitted to a new receiving terminal, a method has been proposed in which other terminals inform the receiving terminal of what transmission rate can be transmitted (for example, patents). Reference 1).

[0014] In this method, when connecting to a new terminal Internet and logging in to a specific server on the Internet (eg, Sano that exchanges instant messages), the bandwidth measurement server on the Internet is used. Used to measure the effective bandwidth between the new terminal and the bandwidth measurement server. Next, the measured effective bandwidth information is notified to another terminal via the specific server. Then, communication is performed between the new terminal and another terminal using this information.

By using this method, it is possible to roughly determine a transmission rate appropriate for streaming performed between a new terminal and another terminal using a value close to the effective bandwidth of the new terminal. Specifically, if the effective bandwidth between the new terminal and the bandwidth measurement server is 1.5 Mbps, the high-definition video transmission with a maximum transmission rate of 6 Mbps is given up. Instead, low-definition video transmission of about 1 Mbps can be performed.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-129205 Disclosure of the invention

Problems to be solved by the invention

[0017] In the conventional method as described above, since the bandwidth between the terminal and the measurement server is measured, the measured value roughly grasps the upper limit of the effective speed of the access line connected to the Internet. It is considered effective. However, this value is not a value obtained by measuring the bandwidth between the transmitting terminal and the receiving terminal that perform streaming, and therefore cannot be applied as the transmission rate (TFRC initial speed) for actual streaming. Specifically, streaming received by a first receiving terminal connected to one in-home router (for example, a display device installed in a kitchen) is sent to a second receiving terminal connected to the same in-home router ( For example, when switching to a display device installed in the living room, the transmission rate received by the first receiving terminal cannot be immediately applied to the second receiving terminal. In other words, the bandwidth between the second receiving terminal and the transmitting terminal is not measured. Therefore, in streaming using TFRC, the transmitting terminal is forced to start slowly, and the transmission rate is Low state power will also start transmission and increase the transmission rate. Therefore, the waiting time after switching until the second receiving terminal can play streaming video or the like becomes longer.

[0018] The present invention has been made in view of the above problems, and a terminal that receives streaming to which transmission rate control using the TFRC algorithm is applied is changed from a first receiving terminal to a second receiving terminal. The present invention provides a communication method and a receiving terminal that can receive and play streaming immediately after switching, without interruption immediately after switching. Means for solving the problem

[0019] The communication method of the present invention is a communication method in which a streaming receiving terminal that performs rate control using TFRC is changed from a first receiving terminal to a second receiving terminal! A determination step of determining that a route on the network between the terminal and the first receiving terminal and a route on the network between the transmitting terminal and the second receiving terminal are the same; A transmission step for transmitting packet loss history information managed by the first receiving terminal to the second receiving terminal when it is determined that the paths are the same. [0020] According to the above configuration, when it is determined that the route is the same, the history information of the packet loss managed by the first receiving terminal is transmitted to the second receiving terminal. The second receiving terminal can immediately receive the streaming at the same transmission rate as that used by the first receiving terminal using the history information transmitted without performing the slow start. Therefore, streaming can be received and played back without interruption immediately after switching the receiving terminal.

[0021] Further, according to the above configuration, a path on the network between the streaming transmission terminal and the first reception terminal, and the network between the transmission terminal and the second reception terminal. Since the history information of packet loss is not transmitted to the second receiving terminal when the route on the network is not the same by determining that the power of the second receiving terminal is the same, the second receiving terminal is inappropriate. It is possible to prevent the network from being congested by receiving streaming at a high transmission rate.

[0022] In addition, the communication method of the present invention adds a second receiving terminal in addition to the first receiving terminal as a streaming receiving terminal delivered by multicast while performing rate control using TFRC. In the communication method, a route on the network between the streaming transmission terminal and the first reception terminal, and a route on the network between the transmission terminal and the second reception terminal The packet loss history information managed by the first receiving terminal to the second receiving terminal when it is determined that the route is the same. And a transmission step for transmitting.

[0023] According to the above configuration, when it is determined that the route is the same, the history information of the packet loss managed by the first receiving terminal is transmitted to the second receiving terminal. The second receiving terminal can immediately receive the streaming at the same transmission rate as that used by the first receiving terminal using the history information transmitted without performing the slow start. Therefore, the streaming can be received and reproduced without interruption immediately after the second receiving terminal is added in addition to the first receiving terminal.

[0024] Further, according to the above configuration, a path on the network between the streaming transmission terminal and the first reception terminal, and the network between the transmission terminal and the second reception terminal By determining that the route is the same, the route on the network is the same. If it is not 1, packet loss history information is not transmitted to the second receiving terminal, so that it is possible to prevent the second receiving terminal from receiving streaming at an inappropriately high transmission rate and putting the network in a congested state. .

[0025] Further, in the communication method of the present invention, when it is determined that the route is the same, the packet loss history information is sent to the first receiving terminal with respect to the transmitting terminal and the second receiving terminal. From the first receiving terminal to the second receiving terminal and the second receiving terminal when the second receiving terminal determines that the route is not the same. A notification step for notifying that the packet loss history information is not transmitted to the receiving terminal and that only the receiving terminal is changed. According to the above configuration, the transmitting terminal and the second receiving terminal can grasp the situation.

[0026] Further, in the communication method of the present invention, the determination step measures a route by a trace route.

[0027] Further, in the communication method of the present invention, the determination step determines that the first receiving terminal and the second receiving terminal are connected to the same network, and transmits the same from the transmitting terminal. It is determined that only one router is connected to the network.

[0028] Further, the receiving terminal of the present invention is a streaming receiving terminal that performs rate control using TFRC, and includes a network path between the streaming transmitting terminal and the own terminal, the transmitting terminal, If there is a determination function that determines that the route on the network to the other receiving terminal is the same, and if the route is determined to be the same, the packet loss history information that is managed by the terminal is displayed. And a transmission function for transmitting to the other receiving terminal.

[0029] Further, the receiving terminal of the present invention is a streaming receiving terminal delivered by multicast while performing rate control using TFRC, on a network between the streaming transmitting terminal and the terminal itself. And the determination function for determining that the route on the network between the transmitting terminal and the receiving terminal newly added as the terminal that receives the streaming is the same as the route A transmission function for transmitting packet loss history information managed by the terminal itself to the newly added receiving terminal when the determination is made. The invention's effect

[0030] According to the present invention, when the terminal that receives the streaming is switched to the first receiving terminal power or the second receiving terminal (or the second receiving terminal is added as the receiving terminal), the terminal is switched (added). ) After that, streaming can be received and played back immediately without interruption. Brief Description of Drawings

[0031] [Fig.1] Explanatory diagram of transmission rate control using TFRC

FIG. 2 is a block diagram showing a configuration of a communication system for explaining the first embodiment (with a call control server).

FIG. 3 is an explanatory diagram for explaining the switching operation of a streaming receiving terminal in Embodiment 1 (in the case of the same route)

FIG. 4 is an explanatory diagram for explaining the switching operation of the streaming receiving terminal in the first embodiment (when it is not the same route)

FIG. 5 is a block diagram showing a configuration of a communication system for explaining the second embodiment (without a call control server).

FIG. 6 is an explanatory diagram for explaining the switching operation of the streaming receiving terminal in the second embodiment (in the case of the same route).

FIG. 7 is an explanatory diagram for explaining the switching operation of a streaming receiving terminal in Embodiment 2 (in the case of not being on the same route)

FIG. 8 is an explanatory diagram for explaining the additional operation of the streaming receiving terminal in the third embodiment (in the case of the same route).

FIG. 9 is a block diagram showing a configuration of a communication system (router having two subnets) for explaining the fourth embodiment.

[Figure 10] A diagram explaining an example of a message containing loss history

Explanation of symbols

[0032] 101 transmitting terminal

102 Sending application

103 Transmission rate controller

104, 206, 306 Call transfer controller 201 First receiving terminal

202, 302 receiving application

203, 303 Loss History Management Department

204, 304 Loss rate reporting department

205 Route Related Information Report Department

207 Same route determination unit

301 Second receiving terminal

305 Route Related Information Report Department

401 router

501 Internet

502 Internet route

601 call control server

701 First network (local network)

702 Second network

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is an explanatory diagram of transmission rate control using the above-described TFRC. This control uses the packet loss history information and round-trip time information measured on the receiving terminal side when application packets are transmitted to the receiving terminal. Control is performed. In the following, an embodiment in which a terminal that receives streaming transmitted from a transmitting terminal that performs transmission rate control using this TFRC algorithm is changed or added will be described.

(Embodiment 1: Centralized control by call control server)

FIG. 2 is a block diagram showing a configuration of a communication system for explaining the first embodiment of the present invention. The communication system shown in FIG. 2 includes a transmission terminal 101, a first reception terminal 201, a second reception terminal 301, a router 401, a call control server 601, an Internet 501 and a local network 701. The Further, the transmitting terminal 101, the call control server 601 and the router 401 are connected to each other via the Internet 501, and the router 401 is connected to the router 401. It is connected to the first receiving terminal 201 and the second receiving terminal 301 via the cul network 701.

The transmission terminal 101 is a terminal that transmits streaming, and includes a transmission application 102, a transmission rate control unit 103, and a call transfer control unit 104. The transmission application 102 is an application that transmits streaming information such as audio and moving images. The transmission rate control unit 103 receives the loss event rate and round trip time information of RTT (Round Trip Time) from the receiving terminal, which will be described later, estimates the band using Equation 1, and based on this, estimates the bandwidth of the transmission application 102. Control the transmission rate. The call transfer control unit 104 transmits and receives call control signaling to and from the terminal and the call control server, and controls the start and end of streaming transmission.

[0037] The first receiving terminal 201 is a terminal that receives streaming. The first receiving terminal 201 includes a receiving application 202 that plays back streamed information such as audio and video on a speaker or a display, a loss information management unit 203 that manages the loss status of received packets, a transmitting terminal Loss detection is performed by monitoring the packet sequence number of the streaming packet sent from 101, and the loss event rate is calculated together with the loss history information managed by the loss history management unit 203. The loss rate report unit 204 that reports the loss event rate to the Internet, the route on the Internet between the transmitting terminal 101 and the own terminal, and the route on the Internet between the transmitting terminal 101 and another receiving terminal are the same. The routing information reporting unit 205 that measures and reports information necessary for the determination and the other terminal or the call control server 601 sends and receives call control signaling, and the stream is reported. And a call transfer control unit 206 for controlling the start and end of the reception of the game.

The second receiving terminal 301 is a terminal that receives streaming in the same manner as the first receiving terminal 201. The second receiving terminal 301 includes a receiving application 302 equivalent to the receiving application 202, a loss history managing unit 303 equivalent to the loss history managing unit 203, a loss rate reporting unit 304 equivalent to the loss rate reporting unit 204, and call control. Call control transfer unit 306 equivalent to transfer unit 206, and determine that the route on the Internet between sending terminal 101 and its own terminal is the same as the route on the Internet between sending terminal 101 and another receiving terminal It is composed of a route related information report unit 305 that measures and reports information necessary for this.

In FIG. 2, a router 401 is a router installed in a home or the like, and receives a first reception. The terminal 201 and the second receiving terminal 301 are connected to the router 401 through the local network 701. The norator 401 is connected to the Internet 501. 502 schematically shows a route on the Internet between the transmitting terminal 101 and the router 401.

[0040] The call control server 601 includes call control transfer unit 104 of the transmission terminal 101, call transfer control unit 206 of the first reception terminal 201, and call control transfer unit 306 of the second reception terminal 301, and call control signaling. Is a call control server that transmits, receives, or relays.

[0041] Next, in the above configuration, a receiving terminal of a stream such as an audio or a moving image whose transmission rate is controlled by the transmitting terminal 101 is transferred from the first receiving terminal 201 to the second receiving terminal 301. The switching operation will be described with reference to the drawings.

FIG. 3 is an explanatory diagram (in the case of the same route) for explaining the switching operation of the streaming receiving terminal in the first embodiment. Figure 3 shows the sequence when switching is performed while using the Session Initiation Protocol (SIP) as a call control sequence transmission / reception system and performing centralized control with the call control server. First, loss history information is notified from the loss history management unit 203 of the first receiving terminal to the call transfer control unit 206. The call transfer control unit 206 of the first receiving terminal 201 sends a switching request message for switching the receiving terminal to the second receiving terminal 301 to the call control server 601. This message includes a URI (Uniform Resource Identifier) that identifies the second receiving terminal 201, an identifier CALL—ID that identifies communication (streaming) currently being performed between the transmitting terminal 101 and the receiving terminal, Information indicating a route on the Internet between the transmission terminal 101 and the first reception terminal 201 and loss history information managed by the loss history management unit 203 are included.

The call control server 601 interprets this switching request message and identifies the second receiving terminal 3 01. Then, the call control server 601 provides the second receiving terminal 301 with information necessary for measuring the route on the Internet between the transmitting terminal 101 and the second receiving terminal 301 as Send the same route confirmation request message including the IP address information. The path-related information report unit 305 of the second receiving terminal 301 that has received the same path confirmation request message uses the IP address information of the transmitting terminal 101 included in the same path confirmation request message, and Measure the route to receiving terminal 301 The Then, the route related information report unit 305 includes the measured route information in the same route confirmation response message, and replies to the call control server 601.

[0044] The call control server 601 that has received the same route confirmation response message uses this route information to send a route on the Internet between the transmitting terminal 101 and the first receiving terminal 201, and the transmitting terminal 101 and the first terminal. It is determined that the route on the Internet between the two receiving terminals 301 is the same. This determination is called determination of route identity. When it is determined that the routes are the same in the path identity determination, the call control server 601 sends a message containing the loss history information of the first receiving terminal 201 to the second receiving terminal 301 (INVITE message in FIG. 3). Notify Then, the call control server 601 transmits to the transmission terminal 101 a transmission rate transfer message (in FIG. 3) describing that the same transmission rate as that of the first reception terminal 201 is applied to the second reception terminal 301. INVITE message).

FIG. 10 is a diagram for explaining an example of a message format including the loss history information. In FIG. 10, 1101 is an example of a header of a SIP (Session Initiation Protocol) INVITE message defined in the Internet standard document RFC2543. 1102 is an example of an Internet standard quick draft—ietf—mmusic—sdp—new—25.txt! An example of a 5L P (Session Description Protocol) format message body. 1103 is a description example of loss history information. 110 4 is a symbol for designating that “attribute” is described in SDP. 1105 indicates an attribute type, and 1106 indicates an attribute value. The attribute value 1106 is described as text separated by commas. 1107 is a character string indicating the number of attributes and the number of attribute values. Each character string separated by commas from 1108 to 1109 is information indicating the loss history.

In this description example, the information indicating the loss history is the number of packets recorded between one packet loss and the next packet loss, that is, the number of packets indicating the loss interval. In other words, the character string delimited by commas from 1108 to 1109 indicates the history of loss intervals. For example, it shows that packet loss occurred after 1024 packets arrived since the first packet loss occurred, and then packet loss occurred again after 2000 packets arrived. Note that the loss history information may be represented by the number of packets received during the occurrence of a loss event, as in this embodiment, or the inverse of this number It may be expressed as a vent rate. Further, the time interval at which the loss event occurs and the reception speed of the streaming data received by the receiving terminal at that time may be transmitted as loss history information. In this embodiment, an example is shown in which eight pieces of loss history information are transmitted. However, the present invention is not limited to this. That is, one or more and a finite number may be sent. In this example, the method of describing the loss history information is shown in accordance with the SDP (Session Description Protocol) format defined in draft-ietf-mmusic-sdp-new-25.txt. The session information is described based on XML (Extensible Markup Language). It may be described in the SDPng format specified in draf t-ietf-mmusic-sdpng-08.txt or in other description methods.

The second receiving terminal 301 that has received the message including the loss history information reflects the loss history information in the loss rate reporting unit 304 and holds a reception history equivalent to that of the first receiving terminal 201. Specifically, the second receiving terminal 301 holds loss interval history information described in 1108 to 1109 shown in FIG. 10 as loss history information. Then, the second receiving terminal 301 uses this loss history information to generate information necessary for rate control by TFRC (that is, a transmission rate transfer message) and transmits it to the transmitting terminal 101. The call transfer control unit 104 of the transmitting terminal 101 that has received the transmission rate transfer message gives the second receiving terminal 301 the same transmission rate as the transmission rate applied to the first receiving terminal 201. The transmission rate control unit 101 and the transmission application 102 are controlled so as to be applied as initial values.

[0047] By operating in this way, first, the transmission terminal 101 to the first reception terminal 201 is about to switch the reception terminal that receives the streaming from the first reception terminal 201 to the second reception terminal 301. The transmission rate applied to the streaming transmission is applied as the initial streaming value from the transmission terminal 101 to the second reception terminal 301. Further, the transmission rate control operation performed between the transmission terminal 101 and the second reception terminal 301 after switching takes over the loss history information of the first reception terminal 201. Therefore, after the receiving terminal is switched, an operation equivalent to the transmission rate control operation performed between the transmitting terminal 101 and the first receiving terminal 201 should be continued between the transmitting terminal 101 and the second receiving terminal 301. Is possible. [0048] Note that the above path identity determination can be realized by using a path determination method called a traceroute for a path between the transmission terminal 101 and the reception terminal. The trace route is a route measurement method that uses a router on the Internet to return ICMP to the source terminal when the TTL (Time To Live) information described in the packet becomes zero. Using this method, it is possible to measure the route on the Internet between specific terminals. Specific operation methods include (1) a method for performing a trace route from the receiving terminal to the transmitting terminal, (2) a method for performing a trace route from the transmitting terminal to the receiving terminal, and (3) a first under specific conditions described later. And a method of confirming that the second receiving terminal is connected via the same router.

[0049] FIG. 3 shows a sequence assuming the method (1), that is, a case where a trace route is performed from the receiving terminal to the transmitting terminal. Similarly, the route identity can also be determined by the method (2), that is, by performing a trace route from the transmitting terminal to the receiving terminal. In this case, first, the call control server 601 transmits the same path confirmation request message including the IP addresses of the first and second receiving terminals 201 and 301 to the call transfer control unit 104 of the transmitting terminal 101. Then, the call transfer control unit 104 may measure the route to the first and second receiving terminals 201 and 301 using the trace route, and return the measurement result in the same route response message.

Note that in this same path determination method, the first receiving terminal 201 and the second receiving terminal 301 are connected to the same local network 701, and pass through the router 401 on the local network 701. If it can be confirmed that there is no route other than the route, it can be realized by a simpler method. In other words, the method described in (3) above is a method for determining that the routes are the same by satisfying two conditions described later. The two conditions are that the local network to which the first receiving terminal 201 and the second receiving terminal 301 are connected is the same (3-1), and that the transmitting terminal 101 to the first receiving terminal 201 Is delivered via the router 401 (3-2). In this method, it can be determined that a local network such as a home network is connected to a single ISP (3-P1), and tunnel communication can be performed for the first and second receiving terminals. Effective when not done (3- P2).

[0051] Note that (3-P1) is confirmed by connecting the first and second receiving terminals to the local network. When continuing, it responds from the response from all routers that are multicast groups that have all router power SJOIN. First, it can be determined by issuing a response request (eg ping6) to all routers (eg ff02:: 2 in the case of IPv6) and confirming that this response is only one router.

In Embodiment 1, the method of including the loss history information in the switching request message has been described. However, in the sequence of FIG. 3, after the path identity determination, the first reception from the call control Sano The terminal 201 may be inquired about loss history information.

FIG. 4 is an explanatory diagram for explaining the switching operation of the streaming receiving terminal in the first embodiment (in the case where the same route is not the same). In the same route determination in the first embodiment, FIG. This is a sequence when it is determined that there is no. In Fig. 4, the sequence up to the same route confirmation response is the same as in Fig. 3. By the same path confirmation response, the call control server 601 uses the Internet path between the transmitting terminal 101 and the first receiving terminal 201 and the Internet between the transmitting terminal 101 and the second receiving terminal 301. It is determined whether the route is the same route. When it is determined that the routes are not the same, the call control server 601 notifies the second receiving terminal 301 and the transmitting terminal 101 that the streaming transfer has been performed without taking over the transmission rate (INVITE in FIG. 4). message). Receiving this message, the second receiving terminal 301 initializes the loss history management unit 303 to prepare for receiving streaming from the transmitting terminal 101. The call transfer management unit 104 of the transmission terminal 101 increases the transmission rate according to the TFRC slow start algorithm without applying the transmission rate applied to the first reception terminal 201. As a result, the second receiving terminal 301 cannot reproduce until the streaming transmission rate reaches the target transmission rate after switching, but the switching of the receiving terminal itself can be completed.

[0054] That is, in the transmission rate transfer method of the present embodiment, the streaming receiving terminal that performs transmission rate control by estimating the band based on the packet loss history information and the return time information is the first receiving terminal. The processing procedure of the transmission rate transfer method when changing from 201 to the second receiving terminal 301 includes the following steps. That is, the route on the network between the streaming transmitting terminal 101 and the first receiving terminal 201 and the route on the network between the transmitting terminal 101 and the second receiving terminal 301 are the same. Judgment judgment to determine whether there is When it is determined that the route is the same in step (1) and determination step (1), packet loss history information managed by the first receiving terminal 201 is transmitted to the second receiving terminal 301. When it is determined that the path is the same in step (2) and determination step (1), the first receiving terminal 201 to the second receiving terminal 301 are transmitted to the transmitting terminal 101 and the second receiving terminal 301. 301 is notified that the transmission rate has been inherited, and the first reception is made to the transmitting terminal 101 and the second receiving terminal 201 when it is determined in the determination step (1) that the routes are not the same. A notification step (3) for notifying that the transmission rate is not carried over from the terminal 201 to the second receiving terminal 301, and that only the change of the receiving terminal is performed, and each step (1), (2), ( Change the receiving terminal by 3)!

[0055] According to this configuration, when it is determined that the route is the same, the history information of the packet loss managed by the first receiving terminal 201 is transmitted to the second receiving terminal 301. The second receiving terminal 301 immediately receives the streaming at the same transmission rate as that used by the first receiving terminal 201, using the transmitted history information without performing the slow start. Can do. Therefore, streaming can be received and played back without interruption immediately after switching the receiving terminal.

[0056] According to the above configuration, the network path between the streaming transmission terminal 101 and the first reception terminal 201 and the network between the transmission terminal 101 and the second reception terminal 301 are also described. By determining that the upper route is the same, if the route on the network is not the same, the history information of the packet loss is not transmitted to the second receiving terminal 301. Therefore, it is possible to prevent the second receiving terminal 301 from receiving the streaming at an inappropriately high transmission rate and bringing the network into a congestion state.

(Embodiment 2: Call transfer without a call control server)

FIG. 5 is a block diagram showing a configuration of a communication system for explaining the second embodiment of the present invention.

The communication system shown in FIG. 5 does not include the call control server 601 provided in the communication system shown in FIG. 102, 103, 201, 202, 203, 204, 205, 302, 303, 304, 305, 401, 501, 502, 701 in FIG. 5 are the same as those in FIG. In FIG. 5, the call transfer control unit 104 of the transmitting terminal 101, the call transfer control unit 206 of the first receiving terminal 201, the second The call transfer control unit 306 of the receiving terminal 301 transmits and receives call control signaling with other terminals to control the start and end of streaming reception, and has a different function from that described in the first embodiment. . In addition, the first receiving terminal 201 shown in FIG. 5 replaces the route related information report unit 205 shown in FIG. The same route determining unit 207 is provided for determining that the route on the Internet with the receiving terminal is the same. In other words, the route related information report unit 205 in FIG. 2 has a function of measuring and responding to a route when the transmitting terminal takes the lead measurement, and the first receiving terminal 201 and the second receiving terminal 301 are in the same network. It has a function to confirm that it has the same router 401 in the Internet connection. On the other hand, the same route determination unit 207 is different from the function of the route information report unit 205 in that the receiving terminal has a function of leading the route measurement.

In this configuration, the transmission terminal 101 performs transmission rate control of TFRC. The operation of switching the reception terminal for streaming of audio, video, etc., from the first reception terminal 201 to the second reception terminal 301. I will explain.

FIG. 6 is an explanatory diagram (in the case of the same route) for explaining the switching operation of the streaming receiving terminal in the second embodiment. Figure 6 shows the sequence when SIP is used as the call control sequence transmission / reception method and the switching operation is performed without using the call control server.

First, a REFER (transmission terminal) message for switching the reception terminal is transmitted from the call transfer control unit 206 of the first reception terminal 201 to the call transfer control unit 306 of the second reception terminal 301. This REFER message includes a URI that identifies the transmission terminal 101 and a SUBSCRIBE that requests a status notification. The call transfer control unit 306 of the second receiving terminal 301 that has received the REFER message interprets the REFER message and sends an INVITE message including the meaning of attempting to take over the transmission rate to the transmitting terminal 101. Then, this response is an OK message.

Next, the call transfer control unit 306 of the second receiving terminal 301 returns a NOTIFY message, which is a status notification message corresponding to the SUBSCRIBE message, to the first receiving terminal 201. The call transfer control unit 206 of the first receiving terminal 201 that has received the NOTIFY message It is detected that the call control operation of the second receiving terminal 301 with the transmitting terminal has been normally performed, and then the same path confirmation request message is sent from the same path determining unit 207 to the second receiving terminal 301. send. The route related information reporting unit 305 of the second receiving terminal 301 receives the same route confirmation request message and returns a same route confirmation response message. The same route confirmation request message and the same route confirmation response message are equivalent to those described in the first embodiment. The same route determination unit 207 measures the route between the first receiving terminal 201 and the transmitting terminal 101. When the same route determination unit 207 receives the same route confirmation response message, the route on the Internet between the transmission terminal 101 and the first reception terminal 201, and between the transmission terminal 101 and the second reception terminal 301, The loss history management unit 203 of the first receiving terminal 201 transmits the loss history information to the second receiving terminal 301, and then the call transfer control unit 206. Sends an UNSUBSCRIBE message to stop status notification by NOTIFY.

[0063] Next, since the second receiving terminal 301 has taken over the loss history information, the same transmission rate as that of the first receiving terminal 201 is applied to the streaming to the second receiving terminal 301. An ACK message including a message instructing to transmit is transmitted to the transmitting terminal 101. The call transfer control unit 104 of the transmission terminal 101 that has received this ACK message applies the same transmission rate as that of the first reception terminal 201 to the streaming to the second reception terminal 301 and the transmission rate control unit 103 and the transmission. Control application 102.

By operating in this way, the same path determination unit 207 causes the first receiving terminal 201 to immediately switch the receiving terminal that receives the streaming from the first receiving terminal 201 to the second receiving terminal 301. The transmission rate applied to the streaming transmission from the transmission terminal 101 to the first reception terminal 201 is the same as the transmission rate between the transmission terminal 101 and the transmission terminal. This is applied as an initial value for streaming from the terminal 101 to the second receiving terminal 301. Further, since the transmission rate control operation performed between the transmission terminal 101 and the second reception terminal 301 after the switching is carried over from the loss history information of the first reception terminal 201, the transmission terminal 101 and An operation equivalent to the transmission rate control operation performed between the first receiving terminals 201 can be continued.

FIG. 7 illustrates the switching operation of the streaming receiving terminal in the second embodiment. It is explanatory drawing for clarifying (when it is not the same path | route). FIG. 7 is a sequence in the case where it is determined that the route is not the same in the route determination. In Fig. 7, the sequence up to the same route confirmation response is the same as in Fig. 6. That is, the same path determination unit 205 measures and determines whether the path between the first receiving terminal 201 and the transmitting terminal 101 and the path between the second receiving terminal 301 and the transmitting terminal 101 are the same. At this time, the same route confirmation response causes the first receiving terminal 201 to connect the route on the Internet between the transmitting terminal 101 and the first receiving terminal 201 and between the transmitting terminal 101 and the second receiving terminal 301. If it is determined that the route is not the same as the route on the Internet, the first receiving terminal 201 notifies the second receiving terminal 301 that the streaming transfer is performed without taking over the transmission rate with an UNSUBSCRIBE message. .

The call transfer control unit 306 of the second receiving terminal 301 that has received the UNSUBSCRIBE message initializes the loss history management unit 303 to prepare for streaming reception from the transmitting terminal 101. Then, the call transfer control unit 306 of the second receiving terminal 301 notifies the call transfer control unit 104 of the transmitting terminal 101 that the streaming transfer has been performed without taking over the transmission rate in the ACK message. The call transfer management unit 104 of the transmitting terminal 101 that has received this ACK message increases the transmission rate according to the TFR C slow start algorithm without applying the transmission rate applied to the first transmitting terminal 201. I will let you. As a result, after the switching, the second receiving terminal 301 cannot reproduce until the streaming transmission rate reaches the target transmission rate, but the receiving terminal switching itself can be completed.

[0067] (Embodiment 3: Applied to multicast distribution)

Since the configuration of the communication system for explaining the third embodiment is the same as that shown in FIG. 5, duplicate explanation is omitted. In this embodiment, call transfer control sections 104, 206, and 306 in FIG. 5 transmit and receive call control signaling with other terminals to control the start and end of streaming reception. Functions differ from those described in 1 and 2. The transmission rate control unit 103 receives information on the available bandwidth from the loss rate reporting units 204 and 304 described later, and transmits the streaming of the transmission application in accordance with the slowest speed. Loss rate reporting units 204 and 304 of the first and second receiving terminals 201 and 301 receive The transmission rate is calculated using the RTT between the transmission terminal 101 measured by the terminal and each reception terminal and the loss event rate, and reported to the transmission terminal 101.

[0068] In this configuration, the transmission terminal 101 performs transmission rate control of TFMCC (TCP—Friendly Multicast Congestion Control: References, Inter Draft draft—ietf—rmt—bb—tfmcc-01.txt). About the problem when streaming to the second receiving terminal 301 is newly received from the state where only the first receiving terminal 201 is receiving streaming of audio, video, etc., and the operation to solve this problem explain.

[0069] First, the operation outline and problems of TFMCC will be described. TFMCC is a method that applies the transmission rate control of TFRC to multicast. The part that detects packet loss on the receiving side, manages its history, and calculates the loss event rate using the loss history information is the same as the TFRC operation. In TFMCC, the receiving terminal measures the RTT between the transmitting terminal and the receiving terminal, and the receiving terminal estimates the transmission rate X using Equation 1 using this RTT and the loss event rate. The receiving terminal reports this transmission rate X to the transmitting terminal, and the transmitting terminal transmits the streaming in accordance with the transmission rate of the slowest receiving terminal.

[0070] In normal operation of TFMCC, when a new receiving terminal is added, since slow start is performed, playback cannot be performed until the streaming transmission rate reaches the target transmission rate! / There was a problem!

[0071] Embodiment 3 provides a method that allows continuous reception at the same transmission rate when a new receiving terminal is added in streaming in which transmission rate control of streaming by TFMCC is performed. The operation of the third embodiment will be described with reference to FIG.

FIG. 8 is an explanatory diagram (in the case of the same route) for explaining the additional operation of the streaming receiving terminal in the third embodiment. In the present embodiment, a case where the second receiving terminal 301 is newly joined will be described. That is, in FIG. 8, the first receiving terminal 201 is a receiving terminal that has received streaming until now, and the second receiving terminal 301 is a newly added receiving terminal.

First, an INVITE message including the multicast multicast address information transmitted by the transmitting terminal 101 is sent from the call transfer control unit 206 of the first receiving terminal 201 to the call transfer control unit 306 of the second receiving terminal 301. Send. Call transfer control unit of second receiving terminal 301 After transmitting the response RINGING message, 306 transmits an OK message including the same route confirmation request. The call transfer control unit 206 of the first receiving terminal 201 that has received the OK message transmits an ACK message including loss history information and the same path confirmation response to the second receiving terminal 301. The call transfer control unit 300 of the second receiving terminal 301 that has received the ACK message uses the same path determination unit 207 to transmit the path between the first receiving terminal 201 and the transmitting terminal 101, the second receiving terminal 301, and the transmission. It is determined whether the route between the terminals 101 has the same power. This determination method is the same as the method described in the second embodiment. In the determination result of the path identity, the path on the Internet between the transmitting terminal 101 and the first receiving terminal 201 and the path on the Internet between the transmitting terminal 101 and the second receiving terminal 301 are: If they are the same, the second receiving terminal 301 applies the loss history information to the loss history management unit 303.

After that, the second receiving terminal 301 performs a procedure for receiving the multicast address described in the INVITE message. Specifically, in the case of IPv4, the call transfer control unit 306 includes IGMP (Internet Group Management Protocol) and MLD (Multicast Listener Discovery: Reference RFC 2710, Internet draft draft—holbrook-idmr-igmp v3-ssm-07. txt) participation message (JOIN message) is transmitted and the receiving application, the network interface of the receiving terminal, and the driver are controlled so that multicast data can be received.

By operating in this way, the second receiving terminal 301 can receive a stream transmitted by multicast. At this time, the receivable bandwidth that the second receiving terminal 301 reports to the transmitting terminal 101 is calculated based on the loss history information received from the first receiving terminal 201. As a result, the loss rate reporting unit 303 of the second receiving terminal 301 and the loss rate reporting unit 203 of the first receiving terminal 201 report the same loss rate to the transmitting terminal 101. The transmission rate control unit 103 of the transmission terminal 101 performs control so that the stream is transmitted in accordance with the slowest reception terminal, but the loss rate reported from the first reception terminal 201 and the second reception terminal 301. Since the routes between the transmitting terminal 101, the first receiving terminal 201, and the second receiving terminal 301 are the same, the round trip time is also the same. Therefore, the available bandwidth calculated by Equation (1) is the same numerical value. In other words, Since the second receiving terminal 301 participates in the multicast group while reporting to the transmitting terminal 101 a transmission rate equivalent to that of the first receiving terminal 201, the transmitting terminal 101 does not need to reduce the transmission rate. For this reason, the transmission terminal 101 does not perform a slow start and continues the same control before the second reception terminal 301 receives, so that the transmission rate of the transmission terminal 101 is maintained.

As a result, when a new receiving terminal is added, the first receiving terminal 201 and the second receiving terminal 301 can continuously receive the same transmission rate as an initial value.

[0075] In the third embodiment, streaming is performed by multicast in which a receiving terminal issues a JOIN message to build a distribution tree on the Internet, and TFMCC is used as transmission rate control. Assuming it is used! /, Only 1S Not limited to this method. For example, XCAST (explicit Multicast: reference Y. Imai, M. Shin and Y. Kim, "XCAST6: eXpli cit Multicast on IPv6", IEEE / IPSJ SAINT2003 Workshop 4, IPv6 and Applications, Orland, Jan. 2003), and a congestion control method using sender-initiated multicast as a transmission rate control method (reference: Mamoru Muramoto, Takahiro Yoneda, Fumiaki Suzuki, Yoshihiro Suzuki, Junji Nakamura, This can be realized even when "Proposal of congestion control method in sender-initiated multicast", Internet Conference 200 3 Proceedings pp5- 10, 2003Z10) is applied. Specifically, in the components shown in FIG. 5 of the third embodiment, the second receiving terminal 301 and the first receiving terminal 201 and the first receiving terminal 301 are newly joined in the sequence described using FIG. The second receiving terminal 301 can continuously receive the same transmission rate as an initial value.

It should be noted that the third embodiment can be realized even when the call control Sano 601 described in the first embodiment is introduced and centralized control is performed.

As described above, in the present embodiment, streaming delivered by multicast is received while estimating the bandwidth and performing transmission rate control based on the history information of packet loss and round trip time information. In the transmission rate transfer method when a second receiving terminal is added in addition to the first receiving terminal as a receiving terminal, a route on the network between the streaming transmitting terminal and the first receiving terminal; The network between the transmitting terminal and the second receiving terminal. The packet loss managed by the first receiving terminal when it is determined in the decision step (1) that determines whether the route on the network is the same and the route in the decision step (1) is the same. If the path is determined to be the same in the transmission step (2) for transmitting the history information to the second receiving terminal and the determining step (1), the transmission is sent to the transmitting terminal and the second receiving terminal. If the rate is reported to the first receiving terminal and the second receiving terminal is notified that the route is not the same in the decision step (1), the sending terminal and the second receiving terminal In response to this, each of the steps (1) has a notification step (3) for notifying that the transmission rate is not inherited by the first receiving terminal and that only the receiving terminal is added. ), (2), and (3) are used to add receiving terminals.

According to this configuration, when it is determined that the route is the same, the history information of the packet loss managed by the first receiving terminal 201 is transmitted to the second receiving terminal 301, so that The second receiving terminal 301 immediately receives the streaming at the same transmission rate as that used by the first receiving terminal 201, using the transmitted history information without performing the slow start. Can do. For this reason, streaming can be received and reproduced without interruption immediately after the second receiving terminal 301 is added in addition to the first receiving terminal 201.

[0079] Also, according to the above configuration, the network path between the streaming transmission terminal 101 and the first reception terminal 201 and the network between the transmission terminal 101 and the second reception terminal 301 are described. By determining that the route above is the same, if the route on the network is not the same, the history information of packet loss is not transmitted to the second receiving terminal 301. Receiving streaming at an inappropriately high transmission rate can prevent the network from becoming congested.

[0080] (Embodiment 4: Applicable when multiple networks are connected to the router)

[0081] The communication system shown in FIG. 9 is different from the communication system described in the other embodiments in the connection relation power ^{s of the} network. 101, 102, 103, 104, 201, 202, 203, 204, 207, 206, 301, 302, 303, 304, 305, 306, 401, 501, 502 in Fig. 9 are the same as in Fig. 5. The In FIG. 9, 701 is a first network to which the router 401 and the first receiving terminal 201 are connected, and 702 is a second network to which the router 401 and the second receiving terminal 301 are connected.

In this configuration, a method of realizing the first receiving terminal 201 and switching the receiving terminal to the second receiving terminal 301 using the sequence described with reference to FIG. 6 will be described. The same route determination unit 207 applies the following algorithm in determining the route identity, so that the route on the Internet between the transmission terminal 101 and the first reception terminal 201, the transmission terminal 101, and the second It can be determined that the route on the Internet to the receiving terminal 301 is the same.

[0083] (Route identity determination algorithm)

(Step 1) Confirm the identity of neighboring routers.

(Step 2) Confirm the identity of the route between the neighboring router and the sending terminal.

[0084] Since the identity of the adjacent router and the identity of the route between the adjacent router and the transmission terminal 101 have been confirmed in Steps 1 and 2 above, it is determined that the route on the Internet is the same.

Step 1 above can be confirmed using the trace route described in the first embodiment.

First, the first router (hereinafter referred to as a first hop router) in the result of the trace route from the first receiving terminal 201 to the second receiving terminal 301, and the first receiving terminal 201 to the transmitting terminal 101. Confirm that the first hop router in the trace route result matches. The first hop router in the trace route result from the second receiving terminal 301 to the first receiving terminal 201 and the first hop router in the result of the trace route from the second receiving terminal 301 to the transmitting terminal 101 are Make sure that you do it. Further, it is confirmed that the router is a power unit between the first receiving terminal 201 and the second receiving terminal 301. If you can confirm these three, you can confirm step 1.

Alternatively, step 1 can be confirmed by comparing the trace route result from the transmission terminal 101 to the first reception terminal 201 with the trace route result from the transmission terminal 101 to the second reception terminal 301.

[0087] Note that in the above path identity determination algorithm,! It may be confirmed that the communication terminal 201 and the second reception terminal 301 are not connected to a virtual interface like a tunnel interface. For example, the first receiving terminal 201 and the transmitting terminal 101 communicate with each other without using a virtual interface such as a power lPv6 over IPv4 tunnel, and the second receiving terminal 301 communicates with a specific server on the Internet 501 such as a VPN (virtual private network) tunnel. Assume a case of communication. In this case, the route between the second receiving terminal 301 and the transmitting terminal 101 may be a route via the specific server, unlike the trace route route measured without using the virtual interface. For this reason, in the same route determination algorithm, by adding a step to determine whether the route measurement using the virtual interface and the route measurement using the virtual interface are the same, if the route is not the same, This makes it possible to make an earlier decision. On the other hand, in the case of the same route, it is possible to determine the same route with higher measurement accuracy.

[0088] In the above path identity determination algorithm, step 1 can be confirmed by the following procedure. First, the first and second receiving terminals 201 and 301 issue an acknowledgment request (for example, ping6) to all routers on the first and second networks 701 and 702, respectively. Then, the first and second receiving terminals 201 and 301 receive a response from the router, and ask the sender (router) of the response for a name (eg, Internet draft: dra sat t—ietf—ipngwg—icmp — Name— lookups— 10. Perform a Node Inform Query, [column: DNS (domain name service) IP address or reverse lookup, which is a method to obtain a name by searching this].

[0089] Step 2 can be confirmed using the trace route described in the first embodiment.

By operating in this way, the streaming from the transmission terminal 101 to the first reception terminal 201 immediately before switching the reception terminal that receives the streaming from the first reception terminal 201 to the second reception terminal 301. The transmission rate applied to the transmission is applied as the initial value of streaming from the transmission terminal 101 to the second reception terminal 301. In addition, the transmission rate control operation performed between the transmission terminal 101 and the second reception terminal 301 after switching takes over the loss history information of the first reception terminal 201. As a result, an operation equivalent to the transmission rate control operation performed between the transmitting terminal 101 and the first receiving terminal 201 is continued. Is possible.

[0091] Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. is there.

This application is based on a Japanese patent application filed on January 11, 2005 (Japanese Patent Application No. 2005-003967), the contents of which are incorporated herein by reference.

Industrial applicability

[0092] In the present invention, when the terminal that receives the streaming is switched to the first receiving terminal power or the second receiving terminal (or the second receiving terminal is added as the receiving terminal), the terminal is switched (added). After that, it has the effect of receiving and playing streaming immediately without interruption

This is useful for communication methods and receiving terminals that change the streaming receiving terminal that performs rate control using TFRC (TCP Friendly Rate Control) from the first receiving terminal to the second receiving terminal.

Claims

The scope of the claims

[1] In the communication method of changing the streaming receiving terminal that performs rate control using TFRC from the first receiving terminal to the second receiving terminal,

It is determined that the path on the network between the streaming transmitting terminal and the first receiving terminal is the same as the path on the network between the transmitting terminal and the second receiving terminal. A determination step to:

A transmission step of transmitting packet loss history information managed by the first receiving terminal to the second receiving terminal when it is determined that the route is the same;

A communication method.

[2] In a communication method in which a second receiving terminal is added in addition to the first receiving terminal as a receiving terminal for streaming delivered by multicast while performing rate control using TFRC.

A communication method.

[3] When it is determined that the route is the same, the packet loss history information is transmitted from the first receiving terminal to the second receiving terminal to the transmitting terminal and the second receiving terminal. If it is determined that the routes are not the same, the packet loss is transmitted from the first receiving terminal to the second receiving terminal to the transmitting terminal and the second receiving terminal. A notification step for notifying that the history information is not communicated and that only the receiving terminal is changed, and

The communication method according to claim 1 or 2, comprising:

[4] The communication method according to any one of claims 1 to 3, wherein the determination step measures a route by a trace route.

[5] In the determining step, the first receiving terminal and the second receiving terminal are the same network. 5. The method according to claim 1, wherein it is determined that the router is connected to the network, and it is determined that only the router is connected to the same network from the transmitting terminal. Communication method.

[6] A streaming receiving terminal that performs rate control using TFRC.

A determination function for determining that the route on the network between the streaming transmitting terminal and the own terminal and the route on the network between the transmitting terminal and another receiving terminal are the same;

A transfer function for transmitting packet loss history information managed by its own terminal to the other receiving terminal when it is determined that the route is the same;

Receiving terminal.

[7] A streaming receiving terminal that is distributed by multicast while performing rate control using TFRC.

The route on the network between the streaming sending terminal and the own terminal is the same as the route on the network between the sending terminal and the receiving terminal newly added as a terminal that receives the streaming. A determination function for determining

A transfer function for transmitting packet loss history information managed by the own terminal to the newly added receiving terminal when it is determined that the route is the same;

Receiving terminal.